Ergonomic equipment arm

ABSTRACT

A mounting arm is disclosed on one end of which a piece of electronic or other equipment is mounted and the other end of which is detachably fastened to the edge of a supporting surface. The arm has three moving joints that permit the equipment fastened thereto to be moved with multiple degrees of freedom for desired positioning of the equipment. One joint utilizes a friction washer assembly and a preloaded torsion spring counterbalancing the weight of the equipment. The torsion spring tension is adjustable to compensate for differing weights of equipment on the one end of the arm. Another joint utilizes a friction ball joint arrangement having double concentric friction ball surfaces in an assembly that permits multiple degrees of freedom of motion and is easily removed from the remainder of the arm without disassembling the ball joint.

This is a continuation of co-pending application Ser. No. 06/432,598filed on Oct. 4, 1982 now abandoned.

FIELD OF THE INVENTION

The present invention relates to movable arms on which equipment ismounted and supported while being easily moved.

BACKGROUND OF THE INVENTION

Movable arms on which equipment may be mounted are known in the art suchas seen in U.S. Pat. No. 3,030,128 issued Apr. 17, 1962 to K. Versen.The movable arm shown in this patent utilizes three rotating and swiveljoints in conjunction with friction couplings and a torsion spring tocounterbalance the weight of a lamp at the end of the arm. Theinteraction of all these joints and elements permits the lamp at the endof the movable arm to be easily positioned in a large number ofpositions within the reach of the arm, and the lamp will stay in theposition in which it is placed.

There are, however, problems with such prior art movable arms. Eachmovable joint has only two degrees of freedom, and when it is desired toorient the lamp or other equipment in a specific position, there isoften difficulty in that the three movable joints do not cooperativelymove as easily as desired when the lamp or other equipment at the end ofthe arm is moved.

In addition, in some applications it is sometimes desired to change thetype of equipment mounted on the end of the movable arm. In the priorart, the weight of the new equipment must be the same as the weight ofthe original equipment being replaced. If heavier or lighter equipmentis placed on the end of the arm, the counterbalancing forces within thearm are not optimum for the new weight and the equipment sometimes willnot stay in a position in which it is placed. For example, with theheavier piece of equipment the arm will sag when the equipment ismanually positioned and then released. To compensate for this type ofproblem in the prior art, the pressure on friction coupling elements inone or more of the movable joints is increased or decreased. However,when the pressure is increased it is correpondingly harder to positionthe heavier equipment on the end of the arm due to jerky arm movement,with the result being difficulty in positioning the equipment in aprecise position. This is caused by greater forces being required toovercome the increased friction and therefore increasing the tendency toovershoot. Thus, changing pressure on friction couplings to accommodatediffering weight loads on the end of a movable arm is impractical.Accordingly, in the prior art a movable arm is usually designed only fora given weight load on the end of the arm. This has been acceptable inthe prior art as there has not been much demand for movable arms thatcan accommodate differing weight loads.

There is a need in the art for a movable arm that can be used withdiffering weight loads at the end of the arm without any change in theforce required to move the load and without requiring different parts.

There is also a need in the art for a movable arm that can be moved moreeasily than in the prior art.

SUMMARY OF THE INVENTION

The above described problems with prior art movable arms are solved byour novel movable arm. Our novel arm utilizes three movable joints, twoof which are pivoting joints each having two degrees of freedom, and thethird joint is a unique friction ball joint having more than two degreesof freedom, which thereby allows the arm to be moved more easily. Inaddition, we provide means for quickly and easily adjusting the tensionof a torsion spring within one of the joints of our arm to properlycounterbalance differing weights on the end of the arm. This permitsdifferent weights on the end of the movable arm to all be moved withequal ease. Furthermore, we provide a clamp means on the end of ourmovable arm opposite the end on which the equipment is fastened whichpermits our movable arm to be mounted on other than a dedicated supportbase table. This permits greater flexibility and portability. Forexample, with a small computer system or word processor terminal, thevideo display can be mounted on the edge of an existing desk or table.

DESCRIPTION OF THE DRAWING

Our invention will be better understood on reading the followingdetailed description in conjunction with the drawings in which:

FIG. 1 shows the assembly attached to the top of a table and flexiblysupporting a television type monitor;

FIG. 2 is an exploded assembly drawing showing the individual elementsmaking up our novel arm;

FIG. 3 is a bottom view of the base of our arm to show the manner inwhich it controls the maximum swing of the arm;

FIG. 4 is a side view of the base of our arm showing the torsion springadjustment; and

FIG. 5 is a cross sectional view of the assembled friction ball joint atthe end of our arm supporting a piece of equipment such as a videodisplay.

FIG. 6 is a prespective view showing the arm with a computer videomonitor installed.

DETAILED DESCRIPTION

In FIG. 1 is shown an assembled arm in accordance with the teaching ofour invention. Our novel arm is quickly and easily mounted to table 10,which is shown in phantom view by means of a clamp 12. The other end ofour arm is fastened to a piece of equipment 11, also shown in phantomview and, which for the present application is a video display. Our armis made up of clamp 12 which is used to fasten our arm to the edge of adesk or table 10 or to any other mounting surface having an edge towhich the clamp can be fastened. A base 13 is connected to clamp 12 suchthat base 13 can rotate in a plane parallel to the surface of table 10.Base 13 is connected to an arm member 14 via an adjustable torsionspring [not shown] and a friction coupling [not shown], and arm member14 can rotate in a plane perpendicular to the plane of the top of table10. At the outer end of arm member 14 is connected a friction ball jointassembly 15, which is in turn fastened to the base of video display 11.Friction ball joint assembly 15 enables video display 11 to be tiltedforward and backward and from side to side. With friction ball jointassembly 15, video display 11 may be moved to any position, and it willremain in that position without tilting further due to its own weight.Thus, the combination of the different joints in our movable arm coupledwith an adjustable torsion spring and friction coupling provides formultiple degrees of freedom of movement of our novel movable arm andvideo display 11.

In FIG. 2 is shown an exploded view of our novel movable arm showing theindividual components making up the arm. Clamp 12 is partially C shapedas shown to go around the edge of a desk, table or any other mountingsurface, whether that mounting surface be horizontal or other thanhorizontal. Screw means 20 is used to move plate 21 in a verticaldirection to securely fasten clamp 12 onto the edge of a table in amanner well known in the art. The top of plate 21 and its opposingsurface on clamp 12 may have a piece of plastic or other materialfastened thereto to provide friction in contact with the mountingsurface and to prevent marring the mounting surface. Plate 21 has twoconical protuberations 50 and 51 which may be created with conical setscrews in threaded holes. These protuberations 50 and 51 embed in theunderside of table 10 so the clamp will not slip. The top surface ofclamp 12 has a circular recess 22 having a diameter only slightly largerthan circular bottom 26 of base 13. Within recess 22 are located threeholes 24, in one of which is placed a peg 25. The particular one ofholes 24 in which peg 25 is placed determines the rotational travel ofbase 13 on the top of clamp 12 as will be better understood in thedescription for FIG. 3 further in this specification. Holes 24 may alsobe threaded and a set screw turned partially therein to accomplish thesame result as peg 25.

Recess 22 in clamp 12 also has a pivot member 23 mounted thereon whichhas a groove 19 around its periphery as shown. Groove 19 is used tofasten base 13 to clamp 12 as is described hereinafter. Base 13 has ahole 18 vertically therethrough having substantially the same diameteras pivot member 23. Hole 18 may also be oversized with a brass bushingpress fit therein with the inside diameter of the bushing beingsubstantially the same diameter as pivot member 23. Base 13 is mounteddown on clamp 12 with its bottom portion 26 sitting within recess 22 ofclamp 12 and with pivot member 23 coming up through hole 18 of base 13.When in this position, a recessed screw [not shown] is turned inward inthreaded hole 30 through base 13 until the tip of the screw extends intogroove 19 around pivot member 23. There is not an interference fitbetween the screw and pivot member 23. A drop of thread lock sealant maybe added to the thread of a screw to retain it in hole 30 withoutloosening. With the screw mounted in hole 30 as just described, base 13cannot be removed from clamp 12 but can rotate about pivot member 23. Anylon piece [not shown] may be placed in recess 22 before base 13 isassembled to clamp 12 to aid in movement of base 13.

Base 13 also has a pivot member 27 which is coaxial with and mountswithin hole 36 through arm member 14 when arm member 14 is assembled tobase 13. The diameter of hole 36 and pivot member 27 are substantiallythe same. Again, a brass bushing may be used in hole 36. In assembly,torsion spring 28, partially wound to provide tension, is mounted overthe outside of pivot member 27, and arm member 14 is then mounted upagainst base 13 on pivot member 27. When arm member 14 is mounted upagainst base 13, wound torsion spring 28 is captivated between these twomembers. Hook end 49 of torsion spring 28 is captivated by a boss [notshown] within the back side of arm member 14. Hook end 48 of torsionspring 28 crosses the axis of threaded hole 29 through base 13 and iscaptivated by a boss 53 [not shown in FIG. 2, but shown in FIG. 4] onbase 13 to prevent torsion spring 28 from unwinding. A recessed screw 54[not shown in FIG. 2, but shown in FIG. 4] within threaded hole 29 hasthe tip of the screw hitting hook end 48 of torsion spring 28. As thescrew [not shown] is screwed further within hole 29, it pushes againsthook end 48 of spring 28 to increase the torsion loading of spring 28and thereby provides an effective means to adjust the torsion loading ofspring 28 to compensate for different weight loads attached to the outerend of arm member 14 via friction ball joint assembly 15. Initially,screw 54 in hole 29 is set to push hook end 48 away from lip 53 [shownin FIG. 4], and thereafter the torsion of spring 28 may be increased ordecreased by turning screw 54.

Arm member 14 is held assembled to base 13 in the following manner. Afriction screw 17 has a broad head 32 and a threaded shaft 34 whichpasses through friction washer 31, wave washer 16, cork washer 50 andthen through hole 36 at the bottom end of arm member 14. Threaded shaft34 then passes through torsion spring 28 and into threaded hole 35 inthe end of pivot member 27 on base 13. Head 32 of friction screw 17 hasa diameter only slightly smaller than the diameter of a recess 37 in thebottom end of arm member 14. On assembly, the screw captivates washers16, 50 and 31 within recess 37 and fastens arm member 14 onto base 13.Head 32 of friction screw 17 has two edge recesses 33, and a spannerwrench is utilized to tighten screw 17. As screw 17 is tightened againstwashers 16, 50 and 31, friction is created against the movement of armmember 14 about pivot member 27 due to the function of the washers. Theouter end of arm member 14 has a hole 47 therethrough and a plurality ofmounting holes 41 as shown. On assembly, screws coming up throughthreaded holes 41 from the bottom of arm member 14 will be turned intorespective ones of threaded holes 40 through the flange of middlefriction member 39 of our novel friction ball joint 15. This is shown ingreater detail in FIG. 5. In this manner, middle friction member 39 isattached to the outer end of arm member 14. The rest of our novelfriction ball joint 15 comprises an upper friction member 38, afastening screw 45, a lower friction member 42, a spring 43, a flatwasher 44, and a nut 46. The diameter of hole 47 through the outer endof arm member 14 is greater than the diameter of lower friction member42, spring 43, flat washer 44, and nut 46. The holes through upperfriction member 38 and lower friction member 42 each have a diameteronly slightly larger than the diameter of the shaft of screw 45.However, the hole 50 through middle friction member 39 is significantlylarger than the diameter of the threaded shaft of screw 45. The concavebottom of upper friction member 38 is spherical and has the same radiusand center point of curvature as the convex spherical top of middlefriction member 39. The concave bottom side of middle friction member 39is also spherical, has a radius of curvature equal to that of the convexspherical top of lower friction member 42, and has a common center pointof radius as all the spherical surfaces. On final assembly, thespherical top of lower friction member 42 is mounted up inside thespherical surface in the bottom of middle friction member 39, and thespherical top surface of member 39 is mounted up inside the sphericalsurface in the bottom of upper friction member 38, such that allspherical surfaces are free to move about the common center point. Onassembly, nut 46 is screwed onto the threaded end of screw 45 and isscrewed down to apply pressure via washer 44 and spring 43 to holdmembers 38, 39 and 42 against each other as is shown in greater detailin FIG. 5. Depending upon how tightly bolt 46 is screwed onto the shaftof screw 45, the degree of friction created between the spherical matingsurfaces of elements 38, 39 and 42 may be varied to create our noveldouble surface friction ball joint 15. Upper friction member 39 isattached to video display 11 or may be an integral part of the base ofvideo display 11. As video display 11 is tilted forward, backward or toeither side, elements 38, 45, 42, 43, 44, and 46 pivot while member 39remains in a fixed position attached to outer end of arm member 14. Thefriction between the assembled elements 38, 39 and 42 permit the videodisplay 11 to be moved into a position and remain in that position.

Turning now to FIG. 3, there is shown a bottom view of base 13. In thebottom of base 13 are located three grooves 50, 51, and 52 which liealong the periphery of circles having different radii. When base 13 isassembled to clamp 12, each of grooves 50, 51 and 52 sit directly overone of the three holes 24 in recess 22. As previously mentioned, peg 25is inserted into one of holes 24 and extends upward out of the hole asshown in FIG. 2. The portion of peg 25 protruding up from a hole 24extends into one of grooves 50, 51 and 52. In particular, when peg 25 islocated in the one of holes 24 closest to pivot member 23 of clamp 12,the top of peg 25 protrudes into groove 52. Rotation of base 13 isthereby limited to ninety degrees in one quadrant. When peg 25 ismounted in the middle one of holes 24 of base 12, its protruding endextends into groove 51 to restrict rotation to 90 degrees in a differentquadrant. With peg 25 being located in the outer one of the three holes24, it extends into groove 50 which allows for 180 degrees rotation ofbase 13 about pivot member 23 of clamp 12. It would be obvious to oneskilled in the art that the position and length of these grooves may bevaried to suit particular applications or may be eliminated allowing afull 360 degrees rotation.

FIG. 4 is a side view of base 13 showing the aforementioned lip or boss53 against which hook end 48 of partially wound torsion spring 28 sitswhen spring 28 is assembled between base 13 and arm 14 on assembly ofthe arm. Hook end 48 extends downward and is in line with the axis ofhole 29 through base 13 and screw 54 therein, the tip of which contactshook end 48. The tension of torsion spring 28 is increased by turningscrew 54 into threaded hole 29 through base 13. Screw 54 is screwed intopush hook end 48 of spring 28 away from lip 53 to set an initial tensionin torsion spring 28. As different weight loads are attached to theouter end of our novel arm, screw 54 is screwed in or out to change thetension of torsion spring 28, to compensate for the different weightloads. For lighter weight loads on the end of our novel arm, screw 54 isunscrewed to decrease the tension of torsion spring 28. For heavierweights on the end of our arm, screw 54 is screwed into hole 29 tofurther wind tension spring 28 and thereby increase the torsion tocompensate for the increased weight load.

FIG. 5 shows the above described details of our novel friction balljoint 15 with the ball joint being in an assembled state. The outer endof arm member 14, having hole 47 therethrough, is only partially shown,with its mounting holes 41 being aligned with the holes 40 through theflange of middle friction member 39, and which is fastened to arm 14 viascrews through each pair of holes 40 and 41. Thus, member 39 is affixedto arm member 14. Upper friction member 38 is an integral part of or isattached to video display 11 [not shown]. It can be seen how thespherical inner surface of upper friction member 38 matches the convexspherical surface of middle friction member 39. It can also be seen howthe concave spherical surface of member 39 mates with the convexspherical surface of lower friction member 42 and all spherical surfaceshave a common center point of radii. In assembly, nut 46 is fastened tobolt 45 as shown and applies pressure via washer 44 and spring 43against lower friction member 42. This spring action forces members 38,39 and 42 together so that there is a friction coupling as well as aball joint function being accomplished between members 38, 39 and 42 asshown in FIG. 5. As video display 11 [not shown in FIG. 5] is tiltedforward, backward or from side to side, the ball joint friction members38, 39 and 42 rotate against each other with a friction coupling. Thisfriction coupling permits the video display 11 to be tilted to a certainposition and then to stay in that position. The degree of frictioncoupling in our novel friction ball joint depends upon the nature of thematerials and the amount of force transmitted through spring 43 toelements 38, 39 and 42 when turning nut 46 onto bolt 45.

While what has been described above is the preferred embodiment of ourinvention, it would be obvious to those skilled in the art that numerousvariations may be made therein without departing from the spirit andscope of our invention. For instance hole 51 through middle frictionmember 39 may be oval or any other shape and limit the degree to whichvideo display 11 [not shown in FIG. 5] may be tilted. In addition,spring 43 in our friction ball joint 15 may be eliminated and pressureapplied directly by nut 46. Further, it should be realized that frictionball joint 15 may be modified to eliminate one of the spherical frictionsurfaces.

What we claim is:
 1. An arm supporting a computer video monitor on anordinary desk or table and allowing the monitor to be moved intodifferent orientations, comprisinga computer video monitor, and an armsupporting said computer video monitor, said arm comprising an armmember having a base end and a monitor end, a base adapted to bedetachably secured to the ordinary desk or table, a first rotatablejoint rotatably connecting said base to said base end of said armmember, for permitting rotation of said arm member with respect to thedesk or table, said first rotatable joint being adapted to permitrotation about vertical and horizontal axes, a friction memberassociated with said first rotatable joint to cause friction in therotation about the horizontal axis of said first rotatable joint, acounterbalance attached to said arm member to support the weight of themonitor and to interact with said friction member to cause the supportedmonitor to stay in any desired one of a plurality of vertical positionsabove the desk or table, while also allowing the monitor to be movedeasily by hand among said plurality of vertical positions, and a secondrotatable joint at said monitor end of said arm member for permittingrotation of the supported monitor with respect to said arm member, saidsecond rotatable joint being adapted to permit rotation of said monitorabout vertical and horizontal axes to permit said monitor to be rotatedrelative to said arm member into any desired one of a plurality ofpositions and remain in said desired position.
 2. The apparatus of claim1 wherein said counterbalance comprises a spring.
 3. The apparatus ofclaim 1 wherein said counterbalance comprises a torsion spring installedat said first rotatable joint between a first and a second housingadapted for relative rotation with respect to one another.
 4. Theapparatus of claim 3 wherein adjustment means are provided for movingone end of said torsion spring while holding the other end fixed toadjust the torque of said torsion spring to compensate for variation inthe weight of the monitor.
 5. The apparatus of claim 4 wherein saidspring is helical and wherein said adjustment means comprises a screwmeans extending through one said housing with one end of said screwmeans touching said one end of said spring, said screw means beingadapted so that as it is wound it moves said one end of said torsionspring so as to either increase or decrease the torque of said spring.6. The apparatus of claim 1 wherein said base comprises a clamp fordetachably securing said base to the edge of said desk or table, saidclamp having a first horizontal surface for resting on the upper surfaceof said desk or table, and a second horizontal surface adapted to beclamped against the undersurface of the edge of said desk or table. 7.The apparatus of claim 6 wherein said second horizontal surface of saidclamp has protuberances adapted to engage and grip the edge of said deskor table.
 8. The apparatus of claim 1 wherein said second rotatablejoint comprises a frictional ball joint permitting rotation in twodegrees of freedom.
 9. The apparatus of claim 8 wherein said frictionalball joint comprises mating convex and concave spherical surfacessqueezed together by a fastening means.
 10. The apparatus of claim 9wherein said mating spherical surfaces are provided by clamping threeelements together, a spherically-shaped middle shell positioned betweeninner and outer elements providing mating convex and concave surfaces,respectively.
 11. The apparatus of claim 10 wherein said three elementsare clamped together by a bolt passing between said inner and outerelements and through an aperture in said middle shell.
 12. The apparatusof claim 1 wherein said friction member comprisesa friction screw havinga wide head and a screw shaft passing through said first housing andthreadably coupling to said second housing, and at least one frictionwasher between the head of said friction screw and said second housing.13. The apparatus of claim 12 wherein said friction washers comprise aplastic washer and a cork washer on either side of a wave washer.